Triiodothyronine (T3)

A T3 test is performed as part of an evaluation of thyroid function. It measures the blood level of the hormone T3 (triiodothyronine), some of which are produced directly by the thyroid gland.

And most triiodothyronine in the blood, however, is produced elsewhere in the body where T4 (the major thyroid hormone produced by the thyroid gland) is chemically converted to T3. Triiodothyronine helps control many body functions including growth, body temperature, and heart rate.

The T3 total test, the most common type of T3 blood test. So T3 measures both the bound and free forms of triiodothyronine in your child’s blood.

But there is no special preparations are needed for this test. However, certain medications, including seizure medication, steroids, and birth control pills, can affect the results, so it’s important to tell the doctor about any medication your child is taking.

And the blood sample will be processed by a machine. So the results are commonly available after a few hours or the next day.

On the day of the test, having your child wear a T-shirt or short-sleeved shirt can make things easier for the technician drawing the blood. (

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